Reactance neutralizing network



June 26, 1928.

J. s. STONE REACT ANCE NEUTRALI ZING NETWORK original Filed Nov. 50.1920 11v VEN TOR Jlm/ 560M Sim/Le B y L W TTORNE y ing application,Serial No. 427, 92,

Patented June 26, 1928.

I warren startl rennet JOHN STONE STONE, OF SAN DIEGO, CALIFORNIA,ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH CGIVIPANY, A CORPORATIONOF NEN YORK.

REACTANCE NEUTRALIZING NETWORK.

Original application filed November 30, 1920, Serial No. 427,392.Divided and this application filed May 27 Serial No. 112,117.

It is an object of my invention to provide a network comprising as a.part thereof a given circuit element having reactancc so that thenetwork as a whole shall have zero reactance over a certain desiredfrequency range.

- This application is a division of my pendfiled November 30, 1920, fora circuit for passing or stopping a frequency band of alternatingcurrents. In that case I have disclosed a network to be interposedbetween a source of electromotive force and apparatus connected incircuit therewith, this network being c e signed to present anapproximately uniform high or low impedance over a certain fre quencyrange and an impedance of opposite character for frequencies outsidethat range.

In the design of such an interposed network it is desirable that thedevice to which the current is to be supplied from the source shall havesubstantially zero reactance over the intended frequency range, and inthat case I have disclosed a combination of apparatus to get such azeroreactance. This combination forms the subject matter of the presentdivisional application.

Referring to the drawings, Figure 1 is a -diagram illlustrating oneembodiment of 1 forms, Lu), (T and a RS, where L stands forinductance,'C for capacity, to is the frequency multiplied by 27., R isresistance and C50 and S are the frequency function and selectance asdefined in the following equations:

o i i Both of these equations have reference to a tuned circuit ofseries inductance L, ca-

pacity C, resistance R and resonant frequency f Of the three forms ofrcactancc mentioned above either of the first two may always be reducedto the third form by supplementing it with proper circuit elements. Whenthe reactance is of the first form, that is when it is a pure inductancereactance, the addition of a capacity react-ance in series will pro ducethe third form. Again, if the initial reactance be ofthe second form,that is if it be a pure capacity reactance, the addition of aninductance reactance in series will produce the third form. And thethird form represented by CCOR-S taken in connection with equations 1and 2 is seen to correspond to the reactance of a resonant circuithaving the resonant frequency f Having reduced the reactance of thecircuit to this last mentioned form additional reactance is chosen andintroduced in series so as to make the resonant frequency f, of theresulting resonant circuit correspond to the medial frequency of theband of frequencies over which the reactance is to be neutralized. Thecombination reached at this stage is represented by the inductance 51and capacity 52 of Fig. 1. The initial reactance may be represented byav part of the inductance 51 or by a part of the capacity but asdescribed above it has been supple mented by further reactance elementsto make the combination of 51 and 52 in Fi 1 having the desired resonantfrequency f In series with the combination 51. 52 and in parallel witheach other are the three elements 53 an inductance, 54 a capacity and 55a resistance. This resistance 55 is shown as the input impedance of athermionic vacuum. tube. For the present it may be thought of merely asa resistance of considerable magnitude, and the reason for showing avacuum tube will become apparent later The reactance of the combination51. 52 is given by the ordinates of curve 1 of F ig. 2, and thereactance of the combination 53. 54, 55 of Fig. 1 is given by the curve2 of Fig. 2. The abscissa: of these curves in Fig. 2 are values of thefrequency function Land 01 and the ordinates of curve 1 are given byequation,

is negligibly small compared to unity the expression reduces to i a xand this reactance will exactly neutralize the reactance of' the seriesresonant circuit when ns x oher the pi. pose of a concrete illustration,let us assume that 0.0-l is the largest quantity which we can rega d asneg 'gible in comparison with uni Accordingly afilfi -Ob l representsthe limiting value of afXf in o si le loop neutralizer, so that in thiswe have A-lQ OiZ. Therefore in the case of the single loop neutralizerwe have these conditions: \;X =O.2 and 118 3 the latter equationreducing to /e r i 1 L where r II no.

and where (1,. L and G, are the capacity, inductance and conductance,respectively, ot the loop. The resistance of this loop throughout theband of width Will be 7 l substantially l Suliiject to the conditionsstated above the esultant reactance of the whole combination shown inFig. 1 is given by the curve 3 of. Fig. 2 whose ordinates are obtainedby adding the ordinates of the curves 1 and 2.

Thus it will be seen in Fig 2 that the Whole combination isapproximately of zero reactance for a. certain rangeof frequencies inthe neighborhood of the freqpency corresponding to zero value for (1Itis believed that the foregoing discussion of an example of the use ofa band reactance neutral-izer will sufiiciently indicate its utility invarious connections. To carry the particular example already discussed alittle further; that is, to make it still more specific, the filamentand grid of an audion have been indicated in Fig. 1.. The most effectivecondition is that in which the con ductance of this translating devicemade the conductance of a band reactance neutrah izor which neutralizesthe reactanee 0a,, RS, of the resonant circuit with which thetranslating device is connected. This mode of connection is the mostefficient possible. The magnitude of the reactance of a loop is notaffected by the algebraic sign of the conductance G so thatthetra-nslating derice may have a negative conductance in which case itbecomes regenerative.

I claim:

1. In combination, a circuit, a device in said circuit having aconsiderable amount of reactance, a supplemental reactance to make thecombination resonant to a desired frequency, and in series With saidcombination a band reactance neutralizer comprising an inductance and acapacity and a resistance in parallel and adapted to neutraL ize thereactance ofsaid combination at and near the said desired frequency.

2. In combination, a circuit, a device in said circuit intended toabsorb energy, also another device in series in said circuit having aconsiderable amount of reactance, a supplemental 'reactance to make thecombina; tion resonant to a desired frequency, and in series with saidreactance combination aband reactance neutralizer comprising aninductance and a capacity in parallel with each other and alsocomprising said first mentioned device in parallel with, said,inductance and capacity and adaptech toneutralize the reactance of saidcombination at and near the said desired frequency.

In testimony whereof, I have signed my name to this specificationthisl8th day of May, 1926.

JOHN STONE STONE.-

